Device for electro-inductive hardening of bearing surfaces and transition radii in crankshafts

ABSTRACT

The invention relates to a device for simultaneous peripheral electro-inductive hardening of bearing surfaces (2A, 3A) and transition A radii in crankshafts (1), comprising lifting pins (2, 3) arranged directly adjacent to each other and one behind the other with different angular positions on the plane perpendicular to the their axis of rotation (D), wherein inductors (8, 9) are provided which are placed on the lifting pins (2, 3) approximately in the same direction (C) thereof. A lifting pin (2, 3) is allocated to each inductor, which is arranged in such a way that it intersects the axial direction of the crankshaft (1). Said inductor comprises at least two inductor detents (8C, 8D, 9C, 9D) arranged parallel to each other. One inductor detent (8D, 9D) is arranged in an overlay area (4) of the lifting pins (2, 3) while the other inductor detent (8C, 9C) is arranged in an edge area of the lifting pin (2, 3) facing a cheek (5, 6). Said inductors are configured with a large inductor segment (8A, 9A) and a short inductor segment (8B, 9B) in such a way that the long inductor segment (8A, 9A) has a width (b --  1) that is larger than half of the overall width (B) of the bearing surfaces (2A, 3A), wherein the long inductor segments (8A, 9A) are always separated by a space (E) in the peripheral direction of the crankshaft (1).

The invention relates to a device for simultaneous peripheralelectro-inductive hardening of bearing surfaces and transition radii oncrankshafts, comprising lifting pins arranged directly adjacent to eachother and one behind the other with different angular positions in theplane perpendicular to the axis of rotation of said crankshafts.

Such devices for electro-inductive hardening of so-called "split-pincrankshafts" which have lifting pins arranged directly adjacent to eachother and offset are sufficiently known from practice in the automotiveindustry, it being endeavored with a number of known designs to hardenthe bearing surfaces of the directly adjacently arranged lifting pins ofa crankshaft simultaneously with little mechanical expenditure and toobtain a desired grain structure.

For example, DE 36 13 309 discloses a method and a device for theinductive hardening of bearing surfaces and transition radii on"split-pin crankshafts", the bearing surfaces and transition radii ofthe lifting pins arranged directly one behind the other beingsimultaneously peripherally hardened by inductors which are arrangedoppositely offset perpendicularly with respect to the axis of rotationof the crankshaft.

This solution offers the advantage that there is considerable spaceavailable for the configuration of the individual inductor and thatmutual inductive influencing of the inductors is avoided. Furthermore,the lateral feeding of the inductors respectively reaching around thelifting pins in a half-shell shape permits maximum wrapping enclosurewithout the inductors touching during rotation of the crankshaft. Withregard to their design, however, the opposite arrangement of theinductors requires relatively great expenditure.

DE 40 01 887 discloses an improved solution with a method and a devicefor hardening crankshafts, comprising pins separated from one another bywebs, the inductors being brought into contact with the pins from thesame side, said pins being narrower than the width of the hardening zoneand the inductors being designed in a known way such that the surfaceregion to be heated to hardening temperature is increased in comparisonwith the width of the inductor and the distance between the inductors ischosen such that the heating-up regions of neighboring inductors mergewith one another.

With the feeding of the inductors from the same direction, preferablyfrom above, this solution requires significantly lower mechanicalexpenditure for hardening. However, to avoid axial contact of theinductors in their region of radial overlap, the angle of wrap of theinductors must be chosen to be shorter than in the case of an oppositefeeding of the inductors, which leads to disadvantages with regard tothe efficiency of the hardening method and the depth of hardening to beachieved by it, in particular uniform hardening of radii.

This restriction also exists with a design of the inductors known frompractice, with portions of different widths, an inductor portion thatserves predominantly for radial hardening covering over half the bearingwidth and a second inductor portion being formed such that it iscorrespondingly narrower, to avoid a collision with the identicallydesigned other inductor. Since the inductor portions in this set-backregion are not effective on the inner radius, there remains, seen fromthe center of the lifting bearing pin, only a maximum effective angle ofwrap of approximately 50°, with which prescribed hardening tolerancescan often be maintained only with difficulty.

The present invention is therefore based on the object of providing adevice of the type stated at the beginning which can be realized interms of structural design in a simple and low-cost way and whichpermits increased efficiency while ensuring optimum hardening of bearingsurfaces and radii.

This object is achieved according to the present invention.

With the device according to the invention, both the advantages ofwrapping a long way around the lifting pins with regard to the hardeningdepth and the advantages of feeding the inductors from one directionwith regard to reduced mechanical expenditure are achieved.

The arrangement according to the invention of the long inductor portionsat a distance from one another in the peripheral direction allows theangle of wrap of the inductor in the overlapping region of the liftingpin periphery to be significantly lengthened, more energy beingintroduced during the same hardening time over the long and widenedinductor portion with its correspondingly long heating path, inparticular into the transition radii, as a result of which a great anduniform hardening depth is made possible there.

Inductors arranged according to the invention can be realized with aportion for the hardening of radii that is over twice as long asconventional inductors with inductor feeding from one direction, forwhich reason, with such a design, for example, a point on the peripheryof the lifting pin is passed over in a certain time interval during nrevolutions of the crankshaft n times, with twice the heating-up length.

To give the device according to the invention high efficiency, in aparticularly advantageous design the long inductor portions may bearranged in such a way that they cover one of the upper quadrants of thelifting pin periphery through at least 60° and the adjoining lowerquadrant through at least 30°, respectively wrapping around the liftingpin periphery preferably in an angular range of 120°.

Further advantageous designs and advantages of the device according tothe invention emerge from the further subclaims and the exemplaryembodiment described in principle below with reference to the drawing,in which:

FIG. 1 shows a plan view in the form of a detail of a crankshaft withinductors of a device for hardening bearing surfaces and radii;

FIG. 2 shows a cross section through the crankshaft according to FIG. 1along the line of intersection A--A of FIG. 1;

FIG. 3 shows a schematized frontal view of the device for hardeningbearing surfaces and radii according to FIGS. 1 and 2;

FIG. 4 shows a schematic plan view of the device for hardening bearingsurfaces and radii; and

FIG. 5 shows a perspective view of an inductor of the device accordingto FIGS. 1 to 4.

In FIGS. 1 to 4, a crankshaft 1 is represented, comprising lifting pins2, 3 arranged directly adjacent to each other and one behind the otherwith different angular positions in the plane perpendicular to the axisof rotation D of said crankshaft, which is also referred to as a"split-pin crankshaft".

The lifting pins 2, 3, arranged offset in relation to each other, eachhave bearing surfaces 2A, 3A, which on one side bound an overlappingregion 4 between the lifting pins, with transition radii not representedany more specifically, and are bounded on the opposite side by a web 5and 6, respectively, of the crankshaft 1.

For the simultaneous electro-inductive hardening of the bearing surfaces2A, 3A and the radii bounding them, inductors 8, 9 are provided,respectively arranged in an inductor housing 7A, 7B and with inductorportions 8A, 8B, 9A, 9B formed as heating loops, the curvature of whichcorresponds to the curvature of the bearing surfaces 2A, 3A and whichare placed onto a respective one of the lifting pins 2, 3 from the samedirection, which can be seen by an arrow C in FIG. 2.

As can be seen in particular in FIGS. 1 and 5, the inductors 8, 9 andthe inductor portions 8A, 9A in each case have two inductor segments 8C,8D and 9C, 9D arranged parallel to each other, of which in each case oneinductor segment 8D and 9D is arranged in the overlapping region 4between the lifting pins 2, 3 and the other inductor segment 8C and 9Cis arranged in an outer region of the lifting pin facing therespectively adjacent web 5, 6.

The heating loops in the inductors 8, 9 are divided and are made in theform of long inductor portions 8A, 9A and short inductor portions 8B,9B. The long inductor portions 8A, 9A are designed in such a way thatthey have a width b₋₋ 1 which is greater than half the total width B ofthe bearing surfaces 2A, 3A.

Since the inductors 8, 9 overlap each other in the axial direction ofthe crankshaft 1, the short inductor portions 8B, 9B are designed with awidth b₋₋ 2 such that during crankshaft rotation they are narrow enoughto slide past even the long inductor portions 8A, 9A with the width b₋₋2 without contact, so that a collision with a possible short-circuit canbe ruled out.

The long inductor portions 8A, 9A, which cover one of the upperquadrants I, II of the lifting pin periphery through at least 50°, inthe present exemplary embodiment through 65°, and the adjoining lowerquadrant III or IV through at least 30°, in the configuration accordingto FIGS. 1 to 5 through 40°, always have in the peripheral direction ofthe crankshaft 1 a spacing E with respect to one another which inanother configuration (not represented) may also be infinitesimallysmall.

This arrangement makes it possible for the long inductor portions 8A, 9Ato be configured with a length with which the lifting pins 2, 3 arerespectively wrapped around by an angle of wrap of 105°.

It can be seen in FIGS. 1 and 5 that the inductor segments 8C, 8D, 9C,9D are designed in the region of the long inductor portions 8A, 9Arespectively as radius hardeners with a lateral outer radius R and areconnected to each other at their free end for power conduction by aconnection 10, 11 designed as a surface hardener.

While the long inductor portions 8A, 9A consequently serve essentiallyfor hardening radii, the short inductor portions 8B, 9B are designed assurface hardeners.

The dimensioning and shaping of the inductor segments 8C, 8D, 9C, 9D, inparticular with regard to their length, results from the respectiveheating-up conditions and the way in which the crankshaft isstructurally designed and can of course be differently chosen in otherexemplary embodiments.

To be able to conduct power through the inductors 8, 9 and for passingcooling water through, inductor segments 8C, 8D, 9C, 9D are connected tofeeds 12, which are designed as pipes.

With reference to FIG. 3, it can be seen that, for supporting andguiding the inductors 8, 9, three sliding shoes 13, 14, 15 arerespectively provided on the lifting pins 2, 3 to be hardened, one ofthe sliding shoes 13, 14, 15 being respectively arranged between theinductor portions 8A, 8B and 9A, 9B as well as at the free ends of theinductor portions 8A, 8B, 9A, 9B. The sliding shoe 15 at the free end ofthe short inductor portion 8B, 9B is in this case arranged in the regionof the bisector of the upper lifting pin quadrant I or II assigned to itand the sliding shoe 13 is arranged offset by 180° at the free end ofthe long inductor portion 8A, 9A.

When viewing the inductor housing 7A, likewise represented in FIG. 3, itcan be seen that in its lower region there is formed a slope 16 forsimple placement of the inductors 8, 9 from one direction onto thebearing surfaces 2A, 3A to be hardened of the lifting pins 2, 3.

Moreover, schematically indicated spray chambers 17, comprising aperforated plate 18 and slot sprays 19, can be seen in the lower regionof the inductor housing for spraying a quenching medium onto the bearingsurfaces 2A, 3A and the adjoining radii to the sides of the inductors 8,9.

We claim:
 1. A device for simultaneous peripheral electroinductivehardening of bearing surfaces and transition radii on crankshafts saidcrankshafts each rotatable about an axis of rotation, said devicecomprising lifting pins arranged directly adjacent to each other and onebehind the other with different angular positions in the planeperpendicular to the axis of rotation of said crankshafts, inductorsbeing provided, which are placed onto the lifting pins from at leastapproximately the same direction and whichsaid inductors respectivelyassigned to a lifting pin and arranged overlapping each other in theaxial direction of the crankshaft, each inductor having at least twoinductor segments arranged parallel to each other, with one inductorsegment of each inductor arranged in an overlapping region of thelifting pins, and the other inductor segment is arranged in an outerregion of the lifting pin facing a web of the crankshaft; each inductorincluding a long inductor portion and a short inductor portion, the longinductor portions partly having a width which is greater than half thetotal width of the bearing surfaces, and; the long inductor portionsbeing arranged to cover an upper quadrant of the lifting pin peripherythrough at least 60°; the long inductor portions having a width which isgreater than half the total width of the bearing surfaces; the longinductor portions have a spacing with respect to one another, in theperipheral direction of the crankshaft, and; the long inductor portionsrespectively covering a lower quadrant of the lifting pin peripheryadjoining the upper quadrants of the lifting pin periphery through atleast 30°.
 2. The device as claimed in claim 1, wherein the shortinductor portions have a width such that the short inductor portions arenarrow enough for the long inductor portions to slide past the shortinductor portions of the other inductor, respectively, without contactduring rotation of the crankshaft.
 3. The device as claimed in claim 1,wherein the inductor segments in the region of the long inductorportions are formed as radius hardeners connected to each other at theirfree end by a connection forming a surface hardener.
 4. The device asclaimed in claim 1, wherein the short inductor portions are formed asbearing surface hardeners.
 5. The device as claimed in claim 1, whereina sliding shoe is respectively arranged between the inductor portionsand the free ends of the inductor portions, the sliding shoe at the freeend of the short inductor portion being arranged at least approximatelyin the region of the bisector of the upper lifting pin quadrant assignedto the short inductor portion and the sliding shoe being arranged offsetby at least approximately 180° in relation to the latter sliding shoe atthe free end of the long inductor portion.
 6. The device as claimed inclaim 1, wherein an inductor housing has a slope in its lower region forplacement of the housing at the inductor portions onto the bearingsurfaces to harden the lifting pins.